I plan on putting a 2element Cubex quad and a Force 12 ef140S rotatable dipole
on a 2"OD 1.5 ID, 6061 T6, 10 ft long.
The calculations of 60% stronger tubing, using the MARC program looks good to
me for this wind load.
Sent from my iPad
Chris k4win
> On Feb 25, 2014, at 8:47 AM, Jim Lux <jimlux@earthlink.net> wrote:
>
>> On 2/24/14 9:39 AM, Chris Pinholster wrote:
>> I have been researching tower mast material. Both aluminum and
>> steel.
>>
>> If aluminum 60601 tubing with 2"OD and .125 wall fails at 35000 ps,
>> what happens when you increase wall thickness?
>
> Not much it might seem, as it happens. The outer part of the wall carries
> the peak stress and fails first (think about holding a bunch of spaghetti in
> your hand and bending it.. which strands break first?)
>
> This kind of thing goes as the 4th power of the radius.
>
> To the first order, you could estimate it as
>
> 1^4 - 0.875^4 =0.414 -> 1/8" wall
>
> 1^4 - 0.75^4 =0.684 -> 1/4" wall
>
> about 60% more strength for about twice as much metal.
>
>>
>> If you increase the thickness of the mast wall, wouldn't that
>> increase make a difference in the bend or failure rating? The charts
>> at the metal company I visited seemed to indicate that would be true.
>> (I was looking at aluminum 2"OD and 1.5"ID)
>>
>> Also I ran across a chart that showed that using a 14 ft mast, with 4
>> ft inside the tower and 10 ft above was stronger than an 11 ft mast
>> with only 1ft inside the tower and 10 ft above.
>>
>> Any opinion or science from this learned group?
>>
>>
>>
>> CHRIS PINHOLSTER k4win@mac.com
>>
>>
>>
>> _______________________________________________
>>
>>
>>
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